[xen stable-4.20] domctl: handle XEN_DOMCTL_{irq,gsi}_permission without acquiring domctl lock

[patchbot@xxxxxxx]

commit d1ffc533650b6f61f5ccdbdf1591143e59feb651
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 4 21:39:31 2026 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Jun 4 21:39:53 2026 +0100

    domctl: handle XEN_DOMCTL_{irq,gsi}_permission without acquiring domctl lock
    
    With dedicated locking added, the domctl lock isn't required here anymore.
    As the GSI handling is in arch-specific code (x86 only), no code is being
    moved there; the 2nd invocation of arch_do_domctl() is re-used. Move the
    re-purposed (XSM_HOOK -> XSM_PRIV, as xsm_domctl() is now bypassed)
    dedicated XSM checks as early as possible.
    
    This is part of XSA-492.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    (cherry picked from commit 6b71151cd84cafff1ea9e67a8022e7a3e41d811f)
---
 xen/arch/x86/domctl.c   |  7 ++++--
 xen/common/domctl.c     | 60 +++++++++++++++++++++++++++----------------------
 xen/include/xsm/dummy.h |  4 +++-
 xen/xsm/flask/hooks.c   |  4 ++--
 4 files changed, 43 insertions(+), 32 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index c772f1f788..3b92690f23 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -265,10 +265,13 @@ long arch_do_domctl(
             break;
         }
 
+        ret = xsm_irq_permission(XSM_PRIV, d, irq, flags);
+        if ( ret )
+            break;
+
         iocaps_double_lock(d, true);
 
-        if ( !irq_access_permitted(currd, irq) ||
-             xsm_irq_permission(XSM_HOOK, d, irq, flags) )
+        if ( !irq_access_permitted(currd, irq) )
             ret = -EPERM;
         else if ( flags )
             ret = irq_permit_access(d, irq);
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 38415ec243..a0f816df55 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -455,8 +455,41 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         goto domctl_out_unlock_domonly;
     }
 
+#ifdef CONFIG_HAS_PIRQ
+    case XEN_DOMCTL_irq_permission:
+    {
+        unsigned int pirq = op->u.irq_permission.pirq, irq;
+        bool allow = op->u.irq_permission.allow_access;
+
+        ret = -EINVAL;
+        if ( pirq >= current->domain->nr_pirqs )
+            goto domctl_out_unlock_domonly;
+
+        irq = domain_pirq_to_irq(current->domain, pirq);
+
+        ret = -EPERM;
+        if ( irq )
+            ret = xsm_irq_permission(XSM_PRIV, d, irq, allow);
+        if ( ret )
+            goto domctl_out_unlock_domonly;
+
+        iocaps_double_lock(d, true);
+
+        if ( !irq_access_permitted(current->domain, irq) )
+            ret = -EPERM;
+        else if ( allow )
+            ret = irq_permit_access(d, irq);
+        else
+            ret = irq_deny_access(d, irq);
+
+        iocaps_double_unlock(d, true);
+        goto domctl_out_unlock_domonly;
+    }
+#endif
+
     case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_ioport_mapping:
+    case XEN_DOMCTL_gsi_permission:
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_unbind_pt_irq:
         ret = arch_do_domctl(op, d, u_domctl);
@@ -788,33 +821,6 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         }
         break;
 
-#ifdef CONFIG_HAS_PIRQ
-    case XEN_DOMCTL_irq_permission:
-    {
-        unsigned int pirq = op->u.irq_permission.pirq, irq;
-        int allow = op->u.irq_permission.allow_access;
-
-        if ( pirq >= current->domain->nr_pirqs )
-        {
-            ret = -EINVAL;
-            break;
-        }
-
-        iocaps_double_lock(d, true);
-
-        irq = pirq_access_permitted(current->domain, pirq);
-        if ( !irq || xsm_irq_permission(XSM_HOOK, d, irq, allow) )
-            ret = -EPERM;
-        else if ( allow )
-            ret = irq_permit_access(d, irq);
-        else
-            ret = irq_deny_access(d, irq);
-
-        iocaps_double_unlock(d, true);
-        break;
-    }
-#endif
-
     case XEN_DOMCTL_settimeoffset:
         domain_set_time_offset(d, op->u.settimeoffset.time_offset_seconds);
         break;
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 2a00a438c8..0b4e1ee9be 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -169,9 +169,11 @@ static XSM_INLINE int cf_check xsm_domctl(
     {
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_getdomaininfo:
+    case XEN_DOMCTL_gsi_permission:
     case XEN_DOMCTL_iomem_permission:
     case XEN_DOMCTL_ioport_mapping:
     case XEN_DOMCTL_ioport_permission:
+    case XEN_DOMCTL_irq_permission:
     case XEN_DOMCTL_memory_mapping:
     case XEN_DOMCTL_unbind_pt_irq:
         ASSERT_UNREACHABLE();
@@ -561,7 +563,7 @@ static XSM_INLINE int cf_check xsm_unmap_domain_irq(
 static XSM_INLINE int cf_check xsm_irq_permission(
     XSM_DEFAULT_ARG struct domain *d, int pirq, uint8_t allow)
 {
-    XSM_ASSERT_ACTION(XSM_HOOK);
+    XSM_ASSERT_ACTION(XSM_PRIV);
     return xsm_default_action(action, current->domain, d);
 }
 
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 5042f7e958..28c681eb34 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -683,9 +683,11 @@ static int cf_check flask_domctl(struct domain *d, 
unsigned int cmd,
     /* These have individual XSM hooks and don't make it here. */
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_getdomaininfo:
+    case XEN_DOMCTL_gsi_permission:
     case XEN_DOMCTL_iomem_permission:
     case XEN_DOMCTL_ioport_mapping:
     case XEN_DOMCTL_ioport_permission:
+    case XEN_DOMCTL_irq_permission:
     case XEN_DOMCTL_memory_mapping:
     case XEN_DOMCTL_unbind_pt_irq:
         ASSERT_UNREACHABLE();
@@ -693,14 +695,12 @@ static int cf_check flask_domctl(struct domain *d, 
unsigned int cmd,
 
     /* These have individual XSM hooks (common/domctl.c) */
     case XEN_DOMCTL_scheduler_op:
-    case XEN_DOMCTL_irq_permission:
     case XEN_DOMCTL_set_target:
     case XEN_DOMCTL_vm_event_op:
 
 #ifdef CONFIG_X86
     /* These have individual XSM hooks (arch/x86/domctl.c) */
     case XEN_DOMCTL_shadow_op:
-    case XEN_DOMCTL_gsi_permission:
 #endif
 #ifdef CONFIG_HAS_PASSTHROUGH
     /*
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.20